Formwork Anchor as well as a Method for Anchoring Formwork Elements and a Method for Removing a Formwork Anchor

ABSTRACT

A formwork anchor comprises a threaded rod, screwable into a thread formed in a first formwork element, a shiftable and exchangeable cone provided on the threaded rod and a removal element that is connectable with the cone and to which a removal force can be applied to remove the cone from hardened concrete. A method for anchoring formwork elements comprises the steps of screwing a threaded rod of a formwork anchor into a thread that is formed in a first formwork element, connecting a shiftable and exchangeable cone provided on the threaded rod with a removal element and shifting the cone and the removal element relative to the threaded rod in the direction of the first formwork element. A method for removing a formwork anchor comprises the steps of removing a threaded rod of the formwork anchor from a thread formed in a first formwork element, whereby a cone provided on the formwork anchor shifts relative to the threaded rod, loosening the cone from the hardened concrete, and jointly removing the threaded rod and the cone.

This application claims priority to German Application No. 102005022335.4, filed May 13, 2005.

FIELD OF THE INVENTION

The invention relates to a formwork anchor as well as to a method for anchoring formwork elements and a method for removing a formwork anchor.

In the field of construction, walls are produced, for example, by positioning two formwork elements so that their formwork surfaces are largely parallel to one another and anchoring them against one another by means of anchors which extend through the concrete which is later filled in. The distance between the opposing formwork elements, and thus the later wall thickness, is furthermore set by the anchors. The anchors must be removable from both the formwork elements that are anchored opposite to one another and from the hardened concrete. A so-called one-sided anchoring is provided in specific cases of use, in which the anchor can be essentially attached and removed on one side, the so-called anchor side, without work steps having to be carried out on the opposite side.

PRIOR ART

Known in this regard as an object of prior use is a formwork anchor called a “Peri-Trio-Housing-Anchor”, which consists of an integral rod, the ends of which are threaded and the middle section of which is designed as a narrow cone. Owing to the thread at the one end, the anchor can be screwed into a nut which is fixed on a first formwork element that is provided on the opposite side. The conical section is located in the region of the area that is later filled with concrete and the cone makes it possible to remove the anchor in the direction of that side at which the cone has the larger diameter. A nut is screwed onto the thread provided at the other end, which acts together with a second formwork element provided on the anchor side and by means of which the desired wall thickness can be set. Such a one-piece anchor is, on the one hand, expensive from the point of view of production engineering. Furthermore, the narrow cone also results in just as narrow elements, so-called plugs, with which the hole remaining in the concrete has to be sealed. These narrow plugs are particularly susceptible to breakage. Finally, the removal of the cone that is integrally provided on the anchor rod from the concrete once it has hardened may cause problems and/or be time-consuming, which affects efficiency.

DESCRIPTION OF THE INVENTION

The object of the invention is to create an improved formwork anchor as well as an improved method for anchoring formwork elements and an improved method for removing a formwork anchor.

This object can be solved on the one hand by means of the formwork anchor described in claim 1.

Therefore, the formwork anchor according to the invention comprises a threaded rod which can be screwed into a thread formed in a first formwork element. The first formwork element is the formwork element that is disposed on the side that is opposite to the anchor side, the so-called opposite side. Since the threaded rod extends through the area that is later filled with concrete to the anchor side, the screwing of the threaded rod into said nut can take place from the anchor side. For this purpose, the threaded rod can be screwed in using a so-called anchor wrench. Alternatively, a coupler can be fixedly connected with, e.g. pressed on, the threaded rod, for example at the end of said threaded rod. The coupler can have an opening, into which a round iron bar or concrete iron bar can be inserted as an actuating lever, and/or a hexagonal profile in order to attach a suitable tool and to screw the anchor rod into the thread formed on the first formwork element. The threaded rod can also be referred to as a threaded cam rod or as an anchor rod. In the case of a threaded cam rod, the contours of the thread are not provided around the entire circumference. The thread contours are rather flattened, for example on two opposite sides, which does not impede use of the thread. The threaded rod is, however, a part of the formwork anchor according to the invention which can be produced in an uncomplicated and inexpensive manner, which is favourable from an economic point of view.

A shiftable and/or exchangeable cone is provided on the threaded rod. The cone is essentially a sleeve-like element which is slipped onto the threaded rod and is provided thereon in a shiftable manner. As a result, the cone can be exchanged for another cone in an extremely simple manner. In particular, different cones can be used for the formwork anchor according to the invention in order to set different wall thicknesses. All the elements of the formwork anchor according to the invention can thus remain unchanged and only the cone has to be exchanged. The cone has an essentially tapered design on its outside so that it can be removed from the hardened concrete in the direction of the side with the larger diameter. The fact that the cone is provided as an element that is separate from the threaded rod and the other elements, as stated below, leads to advantages with regard to the possibility of treating the surface of the formwork anchor according to the invention. Owing to mechanical and chemical stresses in construction, it is desirable to treat the surfaces of such a formwork anchor, for example, by means of electrogalvanisation. However, the cone which contacts the concrete cannot be electrogalvanised since this may lead to chemical reactions with the concrete. In the case of the formwork anchor according to the invention, all of its components, with the exception of the cone, can advantageously be treated in a suitable manner, for example electrogalvanised. The exchangeable cone can be removed for this purpose and remain untreated so that it satisfies the requirements. The described treatment of the other components leads to an increased life of the formwork anchor according to the invention. The components of the formwork anchor can be conveniently made of steel, aluminium, suitable synthetic materials as well as any other suitable materials.

A removal element that can be connected to the cone is furthermore provided on the formwork anchor, to which a removal force can be applied in order to remove the cone from hardened concrete. Removal of the cone from the hardened concrete can prove difficult. In particular, considerable forces are required to remove said cone from the hardened concrete by means of a rectilinear motion, i.e. essentially in the direction of the longitudinal axis of the anchor. If it is attempted to apply this force by turning the threaded rod, using the thread on the opposite side as a support, it may occur that this supports itself on the cone which is stuck in the concrete and that the formwork element of the opposite side is pushed away instead of that support force being applied which leads to the loosening of the cone from the hardened concrete.

During tests in connection with the present invention, it transpired, on the one hand, that removal of the cone can be realised with comparatively little force by first of all turning said cone in the surrounding, hardened concrete. The cone can then be easily pulled out. The described removal element can be designed, for example, such that a removal force is applied in the form of a torsional force that acts on the cone. For example, suitable actuation sections, at which a specific lever arm can be used for the torsional force, may be provided on the removal element for this purpose. Alternatively or additionally, the removal element can, on the other hand, be designed such that a force for removing the cone can be applied in a favourable manner by means of an axial movement, i.e. largely parallel to the longitudinal axis of the anchor. The formwork anchor according to the invention having the described removal element also has advantages in this respect. Tests have shown that the removal force required for removal can be reliably applied. This improved handling can, as mentioned above, be realised in a simply-constructed and inexpensive formwork anchor. Overall, the activities required for erecting and removing the formwork are reduced and simplified, and the formwork anchor according to the invention thus leads to economic advantages in construction engineering.

Preferred developments are described in the further claims.

The removal element can, for example, be connected to the cone by means of a thread. A left-hand thread is hereby preferred since the threaded rod can advantageously have a right-hand thread. As a consequence of a combination of a right-hand thread on the threaded rod and a left-hand thread on the connection between the cone and the removal element, the threaded rod can be removed, for example during removal of the formwork, without simultaneously loosening the connection between the cone and the removal element. However, connection by means of a right-hand thread is also basically conceivable. Furthermore, any other suitable connections between the cone and the removal element can be used.

In order to apply the removal force, the removal element can comprise at least one actuation opening. A concrete reinforcing bar or an anchor rod, which are always present on construction sites, may be inserted into this opening and used as an actuating lever. The torsional force required for removal from the hardened concrete can thereby be applied to the removal element and thus to the cone.

Alternatively or additionally hereto, the removal element may comprise at least one actuation section. The force required for removal can be applied to this section by means of a suitable tool, for example a hammer. This can cause both a turning of the removal element and the cone as well as a translatory shift of the cone in the hardened concrete.

The formwork anchor according to the invention can furthermore comprise a stressing device, by means of which the cone can be pressed against the first formwork element. At the contact point between the cone and the formwork element, there is essentially the aim of sealing this point as well as possible in order to prevent, to the greatest possible extent, concrete from escaping from this region. This contact point can be kept particularly well sealed by the described stressing device. In particular, tests have shown that there is no noteworthy escape of liquid concrete.

The stressing device can be actuated, for example, by means of a nut that works together with the thread of the threaded rod.

At least one resilient member can be advantageously provided between the stressing device and the removal element and/or the cone. The resilient member ensures that the cone closely abuts the first formwork element even during or after filling of the liquid concrete. The liquid concrete that has been filled in namely presses the opposing formworks apart and can lead to a noteworthy extension of the anchor connecting the formworks. If, in the case of such an extension, the cone moves with the anchor, it detaches from the first formwork and the seal would be jeopardised. The described resilient member has the effect that the threaded rod of the anchor may extend, and the stressing device may move at least slightly therewith, in other words its distance from the first formwork element increases. The resilient member acting between the stressing device and the removal element and the cone was, however, pre-stressed in compression during erection of the formwork such that it continues to press the cone against the first formwork element if the described extension of the rod occurs. The seal at this point is thereby ensured in an advantageous manner.

In particular the function described above between the stressing device and the removal element and the cone can basically be realised without these elements having to be connected together. However, it has proven to be advantageous to connect the removal element and the stressing device together in a shiftable manner. This connection improves handlability. The shiftability, which can be ensured despite this connection, makes it possible for the operator to receive feedback to the effect that the cone has reached its position tightly abutting the formwork of the opposite side and that the predetermined wall thickness has been set.

As stated above, the advantages of the formwork anchor according to the invention are achieved also with a single exchangeable cone. Particular advantages with regard to the versatility of the formwork anchor are, however, achieved if said formwork anchor is provided with several cones having different lengths, however having a uniform larger end diameter. Owing to the different lengths, different wall thicknesses can be realised with one and the same formwork anchor by changing the cone. The uniform larger end diameter offers the advantage that the seal between the cone and a second formwork element provided on the anchor side can be realised with simple means. Owing to the uniform larger end diameter, the measures for sealing in this area can namely also be unified, which leads to economic advantages.

The formwork anchor according to the invention can be advantageously combined with a nut that can be fixed to the first formwork element. The thread is essentially formed in the nut, into which the threaded rod of the formwork anchor according to the invention can be screwed. A formwork element can thereby be designed such that it can be used both on the opposite side and on the anchor side. On the one hand, the described nut can be fixed thereon. If this does not occur, the formwork element can be used on the anchor side and can work together with the previously described stressing device of the formwork anchor according to the invention.

It is finally preferred for at least one formwork anchor according to the invention to be provided in combination with at least one formwork element in order to create a complete formwork by way of these components.

The cited object can furthermore be solved by means of the method for anchoring formwork elements as described in claim 12. Formwork elements can be anchored in an efficient manner by means of the cited steps, and the cone used can be easily removed. It is noted that the steps of screwing in the threaded rod on the one hand and connecting the cone with the removal element on the other can be inverted. Preferred further developments of the method for anchoring formwork elements essentially correspond to the preferred further developments of the formwork anchor according to the invention.

Finally, the aforementioned object can also be solved by means of the method for removing a formwork anchor as described in claim 17. This is advantageous since the threaded rod and the cone can be loosened from the formwork element and the hardened concrete separately from one another, however, they can nevertheless be removed together in a simple manner. Removal of the cone can occur in a reliable and quite simple manner by means of a rotational or axial movement.

BRIEF DESCRIPTION OF THE FIGURES

The invention will be explained in more detail below using an embodiment shown in the figures as an example.

FIG. 1 shows a perspective explosive view of the formwork anchor according to the invention;

FIG. 2 shows a perspective view of the formwork anchor of FIG. 1; and

FIG. 3 shows a perspective detailed view of the formwork anchor of FIGS. 1 and 2 in the pre-stressed state.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

It can be seen from FIG. 1 that the formwork anchor 10 according to the invention comprises a threaded rod 12, which can be screwed into a thread (not shown) formed on a formwork element. In the arrangement shown in FIG. 1, the end of the threaded rod 12 that can be screwed into the thread is located at the top left. A coupler 30 having a hexagonal profile 32 and an opening 34 is pressed on at the other end of the threaded rod in the shown embodiment. The hexagonal profile 32 can be used to attach a suitable tool and to screw the threaded rod into the thread or to unscrew it. The opening 34 can be used for the same procedures by inserting an anchor rod, which is normally available on construction sites, into this opening and using it quasi as a rotating lever.

Different elements are slid onto the threaded rod 12. On the one hand, a shiftable and exchangeable cone 14 is provided thereon. This cone has a thread at the larger end, which can be advantageously designed as a left-hand thread 18. Two flattened areas 36 are provided in the vicinity of the thread, of which only the top one can be seen in the figure. A suitable tool can be attached to the flattened areas in order to screw the cone into a thread (not shown) which is provided on a removal element 16.

Just like the cone 14, the removal element 16 is also provided in a shiftable manner on the threaded rod 12 and essentially consists of a sleeve 38 and wings extending radially therefrom on that one end which is facing away from the cone 14. Openings 20 are formed on the wings, preferably at the ends, into which an anchor rod can be inserted in order to be able to remove the cone 14 from hardened concrete, as will be explained in more detail below. Those areas of the wings in which the openings 20 are formed can furthermore be described as actuation sections 22. The reason for this is that an actuating force for removing the cone can be applied to these sections, for example by means of a hammer. This force can be applied in a radial direction in order to remove the cone 14 by means of a rotational movement. It is alternatively possible to apply the force in an axial direction, i.e. essentially in the direction of the threaded rod 12, in order to remove the cone in an axial direction.

Removal of the cone 14 from hardened concrete using the removal element 16 is made possible in that the removal element 16 and the cone 14 are connected. This occurs in the shown embodiment by screwing the left-hand thread 18 formed on the cone 14 into an internal thread, which is not shown, on the sleeve 38 of the removal element 16. In the shown embodiment, two flattened areas 40 (of which the bottom one cannot be seen) are also provided on removal element 16 for this purpose, in particular on the end directed towards the cone 14, in order to attach a suitable tool.

If two formwork elements are anchored together, the threaded rod 12 is, as mentioned above, screwed into a thread that is formed on the formwork element of the so-called opposite side. The cone must abut the inner side of this formwork element as tightly as possible in order to prevent to a large extent concrete from escaping at this point. The formwork anchor according to the invention comprises a so-called stressing device 24 for this purpose. According to the illustration in FIG. 1, the cone 14 is essentially pressed towards the top left by the stressing device and when in use is pressed against the inner side of the formwork element of the opposite side. In the shown embodiment, the stressing device 24 essentially consists of a plate 42 comprising a channel 58 that is directed towards the wings of the removal element 16. In the assembled state, the wings, as can be seen in FIG. 2, are disposed in this channel 58. As can be better seen from FIG. 3, the plate 42 assists support on support elements such as steel beams of the formwork element of the anchor side, on which the stressing device supports itself.

In the shown embodiment, the plate 42 is designed as two separate plates which define the channel 58 disposed therebetween and which are fixed to a disc 46 by means of screws 44. This fixation can also be carried out in another suitable manner, for example by means of welding. This fixation can, in particular, be both removable and non-removable. To some extent, the disc 46 has the negative shape of a ball joint in the vicinity of its central point. The “positive” ball shape is formed on a nut 26 which acts together with the thread of the threaded rod 12. The nut comprises a hexagonal profile 48 on the one hand and wings 50 on the other in order to be able to turn it with respectively suitable tools. Rotating the nut moves the entire stressing device 24 along the threaded rod 12. The ball joint serves to compensate any possible tiltings of the stressing device 24 relative to the threaded rod 12. It is noted that the shown stressing device 24 can be obtained from the applicant under the designation “super plate”.

In the shown embodiment, the removal element 16 is shiftably connected with the stressing device 24 in the following manner. The stressing device 24 is attached to the removal element by means of screws 52, with resilient members 28, in the shown case in the form of small rubber cylinders, being provided therebetween. In the shown example, these are inserted in, for example, circular recesses 54. It must also be mentioned at this point that a first end position between the stressing device 24 and the removal element 16 is defined by the screws 52. However, a second end position results owing to a compression of the resilient members 28, whereby the screws 52 protrude from the disc 46 of the stressing device 24. This is explained in more detail below with reference to FIG. 3.

Shown in FIG. 2 is first of all the assembled state of the formwork anchor described above. The cone 14 and the removal element 16 are connected together and the removal element 16 is connected to the stressing device 24 such that the resilient members 28 located therebetween are at least slightly pre-stressed in compression. The erecting process, wherein two opposing formwork elements are to be anchored, is essentially carried out such that the shown formwork anchor 10 is guided through a suitable opening in the formwork element of the anchor side and through an opening in the formwork element of the opposite side and is then screwed into the thread formed therein by means of its own thread. This occurs, for example, by means of the coupler 30, in particular the contour 32 and/or opening 34 formed thereon. By twisting the nut 26, the entire arrangement consisting of the stressing device 24, the removal element 16 and the cone 14, is subsequently shifted in the direction of the inner side of the formwork element of the opposite side until the smaller end of the cone 14 is abutting against said inner side. The plate 42 and the removal element 16 are thereby supported on support elements, for example beams of the formwork element of the anchor side, whereby the distance between the opposing formwork elements is defined and the thickness of the wall that is later concreted is set.

It can be seen in FIG. 3 how, following pre-stressing of the anchor, the desired state in which the cone 14 closely abuts the inner side of the formwork element of the opposite side can be ensured. The plate 42 is supported on two parallel-extending beams 56 of the formwork element, and the formwork anchor is pre-stressed by twisting the nut 26 of the stressing device 24. In particular the resilient members 28 provided between the stressing device 24 and the removal element 16 are hereby compressed and the distance between the stressing device 24 and the removal element 16 is reduced, preferably to zero, which can be recognised by the protrusion of the screws 52. Owing to this fact, the user can in particular recognise during erection of the formwork that the desired state has been achieved, that the cone 14 is abutting the inner side of the formwork element of the opposite side in a pre-stressed manner and that the predetermined wall thickness has been set.

If concrete is subsequently filled in, it “will attempt to” push the two formwork elements apart and the threaded rod of the formwork anchor may well extend by a few millimetres. In this regard, the nut 26, including the stressing device 24 and the cone 14, may also distance itself from formwork element of the opposite side by a few millimetres. This would cause problems if the cone 14 were thereby to also become removed from its close abutment against the formwork element of the opposite side. However, the resilient members 28 between the stressing device 24 and the removal element 16, which are pre-stressed since they are compressed, continue to reliably press the removal element 16 and thus the cone 14 against the inner side of the formwork element of the opposite side, since they are supported on the stressing device 24. As a result hereof, the heads of the screws 52 may move slightly back towards the disc 46 of the stressing device 24.

Once the filled-in concrete has hardened, the process for removing the formwork essentially begins by unscrewing the threaded rod 12 from the thread formed on the formwork element of the opposite side by way of actuation at its coupler 30. This thread has, for example, a length of 9 cm, and thus the threaded rod is exposed by this distance once it has been unscrewed. However, the cone 14 is normally stuck in the hardened concrete. The arrangement consisting of the cone 14, the removal element 16 and the stressing device 24 therefore initially remains fixed in place relative to the concrete. In the case of the formwork anchor according to the invention, the cone 14 can be loosened by applying a rotational motion to the removal element 16, preferably to the left so as not to undo the left-hand thread between the cone 14 and the removal element 16. The cone thereby frees itself from the hardened concrete and the entire arrangement can be removed from the freshly concreted wall.

The processes for erecting and removing the formwork can both be carried out in a time-saving and efficient manner and the formwork anchor according to the invention is easy to handle since it does not comprise, for example, any losable parts. Furthermore, only the cone 14 has to be exchanged on the formwork anchor in order to be able to concrete a different wall thickness. 

1. A formwork anchor comprising: a threaded rod, screwable into a thread formed in a first formwork element; a shiftable and exchangeable cone provided on said threaded rod, and a removal element connectable to said cone for applying a removal force in order to remove said cone from hardened concrete.
 2. The formwork anchor according to claim 1, wherein the removal element is connectable to the cone by means of a left-hand thread.
 3. The formwork anchor according to claim 1, wherein the removal element comprises at least one actuation opening.
 4. The formwork anchor according to claim 1, wherein the removal element comprises at least one actuation section.
 5. The formwork anchor according to claim 1, comprising a stressing device for pressing the cone against the first formwork element.
 6. The formwork anchor according to claim 5, wherein the stressing device is actuated by means of a nut in conjunction with the threaded rod.
 7. The formwork anchor according to claim 5, wherein at least one resilient member is provided between the stressing device and the removal element and/or the cone.
 8. The formwork anchor according to claim 5, wherein the removal element and the stressing device are shiftably connected with one another.
 9. The formwork anchor according to claim 1, comprising several cones having a different length and a uniform larger end diameter.
 10. The formwork anchor according to claim 1, comprising a nut screwable onto the first formwork element on which the thread is formed.
 11. The formwork anchor according to claim 1 in combination with at least one formwork element.
 12. A method for anchoring formwork elements, comprising the following steps: screwing a threaded rod of a formwork anchor into a thread that is formed in a first formwork element; connecting a shiftable and exchangeable cone provided on said threaded rod with a removal element; and shifting said cone and said removal element relative to said threaded rod in the direction of the first formwork element.
 13. The method according to claim 12, wherein the cone is pre-stressed against the formwork surface of the first formwork element.
 14. The method according to claim 13, wherein during pre-stressing of the cone, at least one resilient member is pre-stressed.
 15. The method according to claim 13, wherein during pre-stressing of the cone, the removal element and a stressing device are shifted relative to one another.
 16. The method according to claim 12, wherein a nut is first fixed to the first formwork element on which a thread is formed.
 17. The method according to claim 13, wherein during pre-stressing of the cone, at least one resilient member is compressed.
 18. The method for removing a formwork anchor, comprising the following steps: removing a threaded rod of the formwork anchor from a thread formed in a first formwork element, whereby a cone provided on said formwork anchor shifts relative to said threaded rod; loosening said cone from a hardened concrete; and jointly removing said threaded rod and said cone.
 19. The method according to claim 18, wherein the cone is loosened by means of rotational or axial movement. 